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Potato adventurer seeks out the world’s spuds

On his potato collecting and identifying treks to the mountains of South America over the past 17 years, University of Wisconsin-Madison researcher David Spooner has had more than his share of adventures. He has ridden horses to remote collection sites, been surprised by sudden mountain storms, and experienced harrowing plane landings on Andean mountaintops. But to the man commonly referred to as the country’s leading potato taxonomist, it’s all in a day’s work.

Spooner, research scientist for the USDA’s Agricultural Research Service and professor of horticulture at the UW-Madison, says he became a botanist because he always dreamed of traveling. He recalls the image that first triggered his wanderlust. In first grade he saw a photograph of a young man leaning against a 1954 Chevy convertible, overlooking a panoramic landscape. “I’m still searching for that picture,” says Spooner. “I wanted to become that person.”

In trying to find that picture, Spooner’s potato research has taken him to many rugged locales. “In Costa Rica, potatoes grow on extremely remote mountaintops in virgin forests that are home to mountain lions and howler monkeys,” Spooner says. “You’ve got to go to extremes to get there, but it is an experience of a lifetime.” Those extremes include elevations of more than 17,000 feet – so high they once gave Spooner double vision and a splitting headache during a hike over a mountain pass between Bolivia and Peru.

Spooner’s potato research has taken him to Argentina, Bolivia, Chile, Colombia, Costa Rica, Ecuador, Guatemala, Honduras, Panama, Peru and Venezuela. On these trips he identifies new wild potato species and collects their germplasm, preserving the biological diversity of potatoes for future potato farmers.

In the United States, 90 percent of the potato crop comes from only a dozen varieties. It wouldn’t take much to completely wipe out the annual harvest. Potatoes are notorious for their susceptibility to bacterial and viral diseases, particularly potato late blight, and to physical stresses, such as cold, drought and insect predation, says Spooner.

“But the beauty of these wild potato species is their resistance to many of these problems,” Spooner says. “In addition, wild potato species have good agronomic traits that improve yields, tastes and colors.”

Those traits in potatoes and other important crops are available to researchers worldwide, thanks to the U.S. National Plant Germplasm System, individual genebanks that are repositories of wild and cultivated crop species. Spooner is the taxonomist for the U.S. Potato Genebank in Sturgeon Bay, Wis. http://www.ars-grin.gov/ars/MidWest/NR6/, which contains 5,000 samples of 140 potato species. Most samples are in the form of true seeds, which can be stored for 25 years or more.

Spooner’s latest project is researching and writing a book on the world’s potato species, part of the genus Solanum. In 2003, Spooner and co-researchers Lynn Bohs at the University of Utah, Sandra Knapp at the Natural History Museum in London, and Michael Nee at the New York Botanical Garden received a 5-year, $4.3 million Planetary Biodiversity Inventory Grant from the National Science Foundation.

One of only four such NSF grants given out in 2003, it was established to encourage researchers to produce definitive keys or identification tools for all of the species within a genus of plants or animals. Spooner and his students are working on potato and tomato (a close relative of potato); his co-researchers are working on other Solanum species.

From a taxonomist’s point of view, potatoes are over-described, Spooner says. Potatoes can look different in different environments, which can cause the same species to have many different names. Spooner is determined to settle the matter. His counterpart in England, Jack Hawkes, published a book on 1990 stating that there were 232 species of potatoes in the genus Solanum. Spooner believes the figure is closer to 150. “Of those,” he says, “we don’t know how many are economically important.”

Although the number of potato species is disputed, their economic importance is not. By some estimates, potatoes are the world’s fourth most important crop, after rice, wheat and corn, in terms of the calories they provide to low-income families. The potato chip industry in the United States alone sells $4 billion worth of product annually. In 1999, domestic per capita consumption of potato products was 144.7 pounds. China grows 25 percent of the world’s crop, while the United States grows 5 percent. One-tenth of the U.S. crop is exported.

There are two parts to Spooner’s data collection for the NSF grant: morphological data and molecular data. The morphology, or appearance, is measured by planting potatoes in experimental fields in Wisconsin, Argentina and Peru. Plant parts such as leaves and flowers are measured and the data are examined by computer-assisted tools that group these plants into species. Spooner and his students also visit herbarium collections in the United States, South America and Europe to gather locality data for this work.

The molecular data include various molecular markers and actual DNA sequences of various genes from a range of species. Together, the two types of data help redefine what a species is and how species are related to one another. Ultimately, Spooner hopes that the taxonomy he devises will have predictive value by grouping related species that share economically valuable traits, such as pest and disease resistance, and agronomic traits, such as the ability to produce better potato chips.

Spooner’s multi-national research team includes five graduate students from Latin America: Diego Fajardo from Colombia; Meche Ames, Flor Rodriguez and Francisco Villamon from Peru; and Alejandrina Alaria from Argentina. In addition, U.S. graduate student McLynda Batterma and USDA biological laboratory technician Sarah Stevenson are also working on various taxonomy projects.

Spooner is also collaborating with colleagues at the International Potato Center and with potato taxonomists and geneticists in Scotland and The Netherlands.

Despite the growing number of low-carb dieters, potatoes are an important dietary staple. One medium-sized potato has about 100 calories and packs a whopping 45 percent of the recommended daily allowance of Vitamin C. Marathon runners and tri-athletes know the importance of eating potatoes: the carbohydrates they contain provide energy, and they are good sources of fiber, potassium and other minerals and vitamins. Spooner is on the Weight Watchers diet, which allows baked potatoes. Make his a Russet Burbank, lightly salted. Hold the butter and sour cream.